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ABSTRACT Global warming is expected to transfer carbon from soil organic matter to atmospheric CO2, with microbial communities playing a crucial role in regulating this exchange. While the immediate impact of temperature on microbial functions is well understood and causes soil carbon losses, the long‐term response remains unclear, with losses stabilising over time, reducing the overall effect of chronic warming on soil organic carbon (SOC) stocks. Here, we examined the temperature dependence of microbial respiration and growth after 9 years of +5°C warming in a temperate forest. Using these temperature dependences and field temperature data, we modelled in situ carbon fluxes and changes in SOC stocks. Results showed that the direct effect of temperature initially increased respiration and growth, projecting a potential 31% SOC stock loss if the trend had persisted. However, the gradual optimisation of microbial traits to warming balanced the direct temperature effects, enhanced carbon use efficiency and offset CO2emissions. Together, these microbial trait shifts limited the heat‐induced SOC loss to 15%, closely aligning with empirical observations. These findings suggest that microbial trait optimisation can moderate carbon emissions, providing a parsimonious mechanistic explanation for observations worldwide and underscoring the need to integrate microbial dynamics into models.
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Thermal Adaptation of Enzyme‐Mediated Processes Reduces Simulated Soil CO 2 Fluxes Upon Soil Warming
Abstract Understanding factors influencing carbon effluxes from soils to the atmosphere is important in a world experiencing climatic change. Two important uncertainties related to soil organic carbon (SOC) stock responses to a changing climate are (a) whether soil microbial communities acclimate or adapt to changes in soil temperature and (b) how to represent this process in SOC models. To further explore these issues, we included thermal adaptation of enzyme‐mediated processes in a mechanistic SOC model (ReSOM) using the macromolecular rate theory. Thermal adaptation is defined here to encompass all potential responses of soil microbes and microbial communities following a change in temperature. To assess the effects of thermal adaptation of enzyme‐mediated processes on simulated SOC losses, ReSOM was applied to data collected from a 13‐year soil warming experiment. Results show that a model omitting thermal adaptation of enzyme‐mediated processes substantially overestimates observed CO2effluxes during the initial years of soil warming. The bias against observed CO2effluxes was lower for models including thermal adaptation of enzyme‐mediated processes. In addition, for a simulated linear 3°C soil warming over 100 years, models including thermal adaptation of enzyme‐mediated processes simulated SOC losses of a factor of three smaller than models omitting this process. As thermal adaptation of microbial community characteristics is generally not included in models simulating feedback between the soil, biosphere and atmosphere, we encourage future studies to assess the potential impact that microbial adaptation has on soil carbon – climate feedback representations in models.
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- Award ID(s):
- 1832210
- PAR ID:
- 10571536
- Publisher / Repository:
- American Geophysical Union
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Biogeosciences
- Volume:
- 129
- Issue:
- 12
- ISSN:
- 2169-8953
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1029/2024JG008619
